In battery/power management applications, PMOSFETs (p-channel metal oxide semiconductor field effect transistors) can be used as high side switches for controlling charging and discharging loops. Since the PMOSFET is usually more expensive than an NMOSFET (n-channel MOSFET) with the same turn-on resistance, sometimes NMOSFETs are used as high side switches. However, if the NMOSFET is used as the high side switch in a battery management circuit, an extra charge pump is needed to drive the NMOSFET. The charge pump may generate relatively high power consumption. Thus, the system power efficiency may be reduced.